I was playing against Computer and checked the Computers King early in the game and then after a few more moves, the Computer "castled" with its King!

 it cannot do this by the rules of Chess!

Is there an error or fault with the Computer progamme?

If it interposed a piece and did not move rook or king then it can later castle. IF the king was still in check or had moved or the rook had moved then bad programming.

Humans are not the only one who can cheat, you know.   They also made my queen disappeared the other day, but I am too lazy to report the bugs.

You need to get the staff here. Preferably you need to post under the Help and Support section.

I always thought that was the rule aswell , but the same thig happened to me. I suspect that we are both wrong and that the rule is that the king cannot castle accross or while in check.

But that old checks are forgotten.

Being in check a few moves ago has absolutely nothing to do with whether or not you can castle now. The king cannot *currently* be in check, end up in check, or slide across a check.  The only rule that has to do with what happened before, is that if you previously move either your king or roook, it takes away your right to castle. (Moved the king or both rooks = no more castle at all either side, moved only one rook = no more castle on that side in future).

Basic chess rules.

The King can't castle while BEING in check, or when the King has moved or the Rook (the one wants to be use to castle) has moved, or there are pieces blocking the path or the King's path is being attacked by the opponent.  However do NOTE that the King can castle even though the Rook's path is attacked. AMaZING isn't it.

BTW there is NO SUCH RULE that once the King is checked, it loses its power to castle.  Never heard of that before!!!

When I was a kid, some people were sure that there was a rule that once your King had been checked, you could no longer castle, but this is just folklore. As long as the King didn't move, it's free to castle.

Another way of phrasing this rule used to be '' you cannot castle out of check '' if king has not moved & checks are later removed then is legal to castle.

I can see how the idea could arise from an incorrect conflation of the two ideas of 1) having to move your king because you're in check, and 2) simply being in check.

Thanks for the replies - seemed to have opened a can of Worms!

I am still not clear whether the King can castle after being checked!

I understand that once the King moves in negates that option.

Has been a while since i played so am clearing the cobwebs.

Merely having been checked previously does not remove castling privileges. Period.

Best if you post the game in here so we can see what really happened.

I concur.

That's not 15, my friend. It's FIFTY!

As you can see here http://www.chess.com/learn-how-to-play-chess.html, castling is perfectly fine even after being checked in a previous position (as long as none of the other constraints is violated, of course).

a lot of home players play with the rule that you cannot castle after being checked. in fact that was what I learned as a child. until I joined a club.
so before that I played to make sure to check my opponent early in order to prevent him from castling.

en passant and castle are two things I guess home players don't use correct. en passant not all.

Lady-in-Red wrote:

What do you mean I couldn't castle???? 

Classic. If only my king can do that in a real game, ... :)

Also, some home players still play with the rule that pawns can only promote to a captured piece! And then there is the famous story of the Soviet Grandmaster who forgot that the Rook, unlike the King, can move across a square that the opponent attacks when Castling.

So, yes, even though the rules of Chess are not all that complicated, sometimes people do get them wrong.

Talking of beginners and castling, my 8-year old nephew recently wanted to play Kxc1 and 0-0-0 at the same time. He thought it was totally unfair he couldn't take the Knight while castling and wanted a logical explanation. Unfortunately I was reduced to saying "Well, you just can't!" Wait till he finds out about en passant ...

also homeplayers play without a chess clock.
it wouldn't work against a club player. a home player doesn't have the patience to wait 5 minutes on a move.
about castling : In a match otb my oppnent forgot he had already castled so he wanted to castle again. I did not realize it in the game but a spectator was awake and stopped him from doing so - but I think the spectator should have been quiet only a TD could say something.
 if nobody said something it could have turned out this way like Wolfgang Heidenfeld and Nick Kerins, in Dublin in 1973. : 1. e4 e6 2. d4 d5 3. Be3 Nf6 4. e5 Nfd7 5. f4 c5 6. c3 Nc6 7. Nf3 Qb6 8. Qd2 c4 9. Be2 Na5 10. 0-0 f5 11. Ng5 Be7 12. g4 Bxg5 13. fxg5 Nf8 14. gxf5 exf5 15. Bf3 Be6 16. Qg2 0-0-0 17. Na3 Ng6 18. Qd2 f4 19. Bf2 Bh3 20. Rfb1 Bf5 21. Nc2 h6 22. gxh6 Rxh6 23. Nb4 Qe6 24. Qe2 Ne7 25. b3 Qg6+ 26. Kf1 Bxb1 27. bxc4 dxc4 28. Qb2 Bd3+ 29. Ke1 Be4 30. Qe2 Bxf3 31. Qxf3 Rxh2 32. d5 Qf5 33. 0-0-0 Rh3 34. Qe2 Rxc3+ 35. Kb2 Rh3 36. d6 Nec6 37. Nxc6 Nxc6 38. e6 Qe5+ 39. Qxe5 Nxe5 40. d7+ Nxd7 0–1